Central heating combi boiler pressure loss

[Elephant14]

Well, after 6 days with the boiler and radiator circuits isolated from each other (using the standard valves on flow and return as well as the extra valves I had put in) the boiler pressure is unchanged at 2.0 bar. I'll leave it two more days, but six days with no change tells me my leak is not in the boiler. It also tells me that one of the extra isolation valves I had put in is leaking.

So on Saturday or Sunday I'll open the flow and return valves, and see what happens to the pressure reading.
Then I'll bleed all the rads, just to be sure they're full, repressure to 2.0 bar and turn on the central heating.

Then for the next half-hour or so I'll go round to all the rads in turn, checking all screw-in joints for leaks. Then I'll turn the CH off, and going round checking again as the system cools.

Questions:
1) Is 2.0 bar repressuring too high? 2.0 bar is the upper limit of Vaillant's recommended range, but normally I keep the cold pressure at 1.4 bar or below. Years of dealing with W-B boiler problems have made me wary of overtaxing the system.
2) Anything else I can do to check the rad circuit? I've already checked ground floor ceiling for water stains and oversite concrete under the ground floor for signs of leaks (the pipes are all insulated there), but will look at those again anyway.
3) I have TRV valves, which I've never had before and know nothing about. Do I just look and finger-check (run my finger saround the joint and check for water) as with other screw-in connections?

[Elephant14]

Update
Thank you for the help to those who offered it.
For those with central heating problems: As stated about I tested the boiler alone by isolating it, and found it retained 2.0 bar pressure for ten days: so the leak was in the radiator circuit.
I lifted floorboards on the (suspended) ground floor and checked on the oversite concrete for water stains: nothing.
I checked the ground floor ceiling for water stains, taking it as an article of faith that a leak in the first floor pipe work would stain the ceiling below. Experienced plumbers confirmed this. After all, I’d been losing 0.3 bar pressure a week for three months. I calculated conservatively that that would release about 5 litres of water. Maybe I got that wrong, but even one litre would leave a stain, right?

Wrong: I lifted the hardboard then the floorboards on the first floor over the pipe runs between the joists: nothing. Then I lifted the boards in front of and parallel to the rads, where the pipes run in notches across the joists. The plumbers always notch the joist under the midwidth of the floorboard, as the nails fixing the board to the joist go near the sides of the board.

But for the rad of the back wall, Muggins, in putting in the internet cables, put in a screw through the middle of the floorboard and down into the copper pipe. And out came the water. To misquote the bard, I caused ‘bubble bubble, toil and trouble’. Toil and trouble it’s been, with a vengeance.

Why didn’t it stain the ceiling below? With lath and plaster it should seep through and stain at the leak position. Even with plasterboard, water in those quantities would seep along till it found a joint, then cause a stain. I had neither. Three months leaking and no stain. The floor joist was wet and had green fungus on it, but I’ll leave the floor open so the timber can dry. The fungus, with no source of moisture, will die. So that’s not a problem here.

What I do have is a ground floor ceiling of (original) lath and plaster with (recent) plasterboard below it. Not a clever solution, as the floor joists, usually undersized by modern standards, are loaded yet further. I’ve always had the plaster of a lath and plaster ceiling removed first, leaving the laths in place, before I have plasterboard put up. Here the previous owner didn’t and this retained the leak water.

So the lesson is don’t rely on stains on the ceiling below a pipe run to reveal a leak

[DrFfybes]

Glad you found the leak - some great detective work.

A couple of observations....

n putting in the internet cables, put in a screw through the middle of the floorboard and down into the copper pipe.

If you're fixing cat5 to the floor, you could probably get away with a shorter screw or even a cable clip, unless the cable is holding up the floor

What I do have is a ground floor ceiling of (original) lath and plaster with (recent) plasterboard below it. Not a clever solution, as the floor joists, usually undersized by modern standards, are loaded yet further.

Very common, esprecially f the original ceiling had artex on which tended to contain asbestos.

Payl

[Elephant14]

Thanks for your reply.
The screw into the pipe had nothing to do with the CAT 5 cable, which just lies loose in the floor void. It just explains why I had the floorboards up.

I had one ceiling replaced, and it wasn't Artexed. The plasterer was astonished and a bit miffed that I wanted the old plaster down first. That suggested to me that the 'just bang it on top' method is usual practice.